Is this correct

[PA3040D]

Dear All have a nice day

As per the image is showing in the last line has minuses letter ( - ) in side the red cycle . That minuses letter is used to remove the minuses in the just above line as shown in the red line

My question - is that the correct way

 

[skeeter]

yes,

[MATH]-x-9 = -(x+9)[/MATH]
even if other separate factors are present.

looks ok to me

 

[HallsofIvy]

I suggest writing that "-" in front as "(-1)".